During the 1990's the telecommunications market experienced two extremely favorable market factors of quickly increasing bandwidth requirements combined with fast market growth. While these factors were great for the industry, they led to a hodgepodge of proprietary standards designed to meet the immediate market needs that each company was working to service. Despite the advent of the highly successful Compact PCI (peripheral component interconnect) standard, the fact remains that the majority of the telecommunications market has no standard form factor, backplane or fabric interconnect that can meet the 10 Gb/sec+ bandwidth requirements of today. There continues to be tens, if not hundreds, of different chassis designs in the telecommunication industry, which drives the cost of this equipment higher, while preventing multi-sourcing and interoperability across a common backplane or fabric.
Significant changes in the telecommunications market have occurred in the last few years, resulting in a leveling off of the meteoric growth of the 1990's, with competition increasing accordingly. In today's cost-cutting environment of constrained budgets, it is more important than ever for telecommunications equipment providers to leverage off-the-shelf components and sub-systems, thereby minimizing investment and maximizing the breadth of product environment.
In view of the foregoing, as well as other considerations, various industry efforts have been directed to defining a standardized, modular telecommunications equipment solution. A leading standard resulting from one of these endeavors is the Advanced Telecommunications Architecture (ATCA) (also referred to as Advanced TCA). The ATCA standard defines an open switch fabric based platform delivering an industry standard high performance, fault tolerant, and scalable solution for next generation telecommunications and data center equipment. The development of the ATCA standard is being carried out within the PCI Industrial Computer Manufacturers Group (PICMG)—the same group that created the highly successful Compact PCI standard. The Advanced TCA 3.0 base specification defines the physical and electrical characteristics of an off-the-shelf, modular chassis based on switch fabric connections between hot-swappable blades. The Advanced TCA base specification supports multiple fabric connections, including the advanced switching (AS) standard.
The ATCA 3.0 base specification defines the frame (rack) and shelf (chassis) form factors, core backplane fabric connectivity, power, cooling, management interfaces, and the electromechanical specification of the ATCA-compliant boards. The electromechanical specification is based on the existing IEC60297 EuroCard form factor, and enables equipment from different vendors to be incorporated in a modular fashion and be guaranteed to operate.
The ATCA 3.0 base specification also defines a power budget of 200 Watts (W) per board, enabling high performance servers with multi-processor architectures and multi gigabytes of on-board memory. The framepower is delivered by redundant −48 VDC feeds. These dual framepower feeds are typically fused and multiple sub-feeds are generated, allowing each shelf to remain electrically isolated. Local DC—DC conversion is accomplished per board. Redundant local power feeds are normally attached through either diode Or'ed connections to a single on-board DC—DC converter or via on-board dual redundant load sharing DC—DC converters.
The PICMG organization has performed extensive thermal modeling in order to design the ATCA board and shelf form factors to be able to support 200 W power dissipation per board slot. In a typical implementation, the shelf uses conventional air cooling, with blowers pulling air from front to rear and bottom to top. Mechanical fans are typically the element with the lowest MTBF (mean time between failure), and thus thermal designs should incorporate sufficient overhead to accommodate a failed blower. Blowers may be synchronized and include temperature controlled airflow to reduce audible levels.
Although the ATCA standard is a step in the right direction, several of its design aspects are limiting. Notably, the 200 W power dissipation per board slot places a restriction on how much heat can be generated by a board, while not defining the location of the heat sources. (It is noted the 200 W limit applies to boards occupying a single slot. Higher power dissipations are allowed for boards occupying multiple slots, e.g., a front board occupying two slots is limited to 400 W). In order to meet ever increasing bandwidth demand, equipment capabilities need to increase, requiring faster processors, among other board component improvements. When considering identical semiconductor fabrication processes, there is a direct relationship between speed and power consumption—the faster the processor speed, the greater the power consumption of the processor, and thus the greater the amount of heat that must be dissipated by an ATCA board hosting the processor. In view of the rigid board and shelf form factors defined by the ATCA base specification, this leads to problems in achieving sufficient cooling for high-power components such as processors, since the majority of the 200 W will be consumed by such components. Power routing on the boards is also problematic.